Complete genome sequences of nine Burkholderia pseudomallei strains

We report the complete genome sequences of nine Burkholderia pseudomallei strains preserved in research facilities in Japan; GTC3P0019, GTC3P0050, GTC3P0054, GTC3P0254T (type strain), Kanagawa, Tokushima, KM376, KM390, and KM391. The genomic information of these strains may provide references for comparative studies of B. pseudomallei pathogenicity.

Genotyping of Mycoplasma pneumoniae strains isolated in Japan during 2019 and 2020: spread of p1 gene type 2c and 2j variant strains

We characterized 118 Mycoplasma pneumoniae strains isolated from three areas of Japan (Saitama, Kanagawa, and Osaka) during the period of 2019 and 2020. Genotyping of the p1 gene in these strains revealed that 29 of them were type 1 lineage (29/118, 24.6%), while 89 were type 2 lineage (89/118, 75.4%), thereby indicating that type 2 lineage was dominant in this period. The most prevalent variant of type 2 lineage was type 2c (57/89, 64%), while the second-most was type 2j, a novel variant identified in this study (30/89, 33.7%). Type 2j p1 is similar to type 2 g p1, but cannot be distinguished from reference type 2 (classical type 2) using the standard polymerase chain reaction-restriction fragment length polymorphism analysis (PCR-RFLP) with HaeIII digestion. Thus, we used MboI digestion in the PCR-RFLP analysis and re-examined the data from previous genotyping studies as well. This revealed that most strains reported as classical type 2 after 2010 in our studies were actually type 2j. The revised genotyping data showed that the type 2c and 2j strains have been spreading in recent years and were the most prevalent variants in Japan during the time-period of 2019 and 2020. We also analyzed the macrolide-resistance (MR) mutations in the 118 strains. MR mutations in the 23S rRNA gene were detected in 29 of these strains (29/118, 24.6%). The MR rate of type 1 lineage (14/29, 48.3%) was still higher than that of type 2 lineage (15/89, 16.9%); however, the MR rate of type 1 lineage was lower than that found in previous reports published in the 2010s, while that of type 2 lineage strains was slightly higher. Thus, there is a need for continuous surveillance of the p1 genotype and MR rate of M. pneumoniae clinical strains, to better understand the epidemiology and variant evolution of this pathogen, although M. pneumoniae pneumonia cases have decreased significantly since the COVID-19 pandemic.

P1 gene of Mycoplasma pneumoniae isolated from 2016 to 2019 and relationship between genotyping and macrolide resistance in Hokkaido, Japan

We characterized 515 Mycoplasma pneumoniae specimens in Hokkaido. In 2013 and 2014, the p1 gene type 1 strain, mostly macrolide-resistant, was dominant and the prevalence of macrolide resistance was over 50 %. After 2017, the p1 gene type 2 lineage, mostly macrolide-sensitive, increased and the prevalence of macrolide resistance became 31.0 % in 2017, 5.3 % in 2018 and 16.3 % in 2019.

A case of renal abscess and bacteremia caused by Burkholderia pseudomallei that was first unidentifiable by matrix-assisted laser desorption ionization-time of flight mass spectrometry in a Japanese-man

Melioidosis, an infectious disease caused by Burkholderia pseudomallei, is endemic in specific regions, including Southeast Asia and Northern Australia. In Japan, where no autochthonous has been reported to date, melioidosis is a rare infectious disease. Herein, we report a case of melioidosis in a 68-year-old Japanese man with renal abscess and bacteremia, but without pneumonia. The patient presented to our hospital and was admitted for fever and chills that have persisted for two months. It was speculated that he was infected in Thailand, where his family lives because he shuttled between Thailand and Japan. Blood cultures on admission identified Burkholderia species; however, the species was unidentifiable by matrix-assisted laser desorption ionization-time of flight mass spectrometry. Further re-examination, including culture, loop-mediated isothermal amplification, and multiplex polymerase chain reaction methods, finally identified Burkholderia pseudomallei. We treated the patient with intravenous ceftazidime for four weeks. In addition to the antibiotics administration, puncture drainage of the renal abscess was performed, and he gradually became afebrile. Intravenous ceftazidime was switched to oral sulfamethoxazole/trimethoprim on post-admission day 32, and he was discharged. After five months of oral sulfamethoxazole/trimethoprim, no recurrence was observed one year after discharge. To diagnose melioidosis, especially in non-endemic areas, a precise and thorough understanding of its epidemiology, presentation, and identification methods is necessary.

Therapeutic efficacy of azithromycin, clarithromycin, minocycline and tosufloxacin against macrolide-resistant and macrolide-sensitive Mycoplasma pneumoniae pneumonia in pediatric patients

OBJECTIVE

To clarify therapeutic effects of azithromycin, clarithromycin, minocycline and tosufloxacin against macrolide-resistant Mycoplasma pneumoniae (MRMP) pneumonia and against macrolide-sensitive Mycoplasma pneumoniae (MSMP) pneumonia in pediatric patients.

METHODS

A prospective, multicenter observational study was conducted from July 2013 to August 2015. The therapeutic effects of azithromycin, clarithromycin, minocycline and tosufloxacin were evaluated in 59 patients with pneumonia caused by MRMP and in 50 patients with pneumonia caused by MSMP. In vitro activities of antimicrobial agents against isolates of Mycoplasma pneumoniae were also measured.

RESULTS

Mean durations of fever following commencement of treatment in patients infected with MRMP and MSMP were 5.2 and 1.9 days, respectively (log-rank test, P < 0.0001). Among patients infected with MRMP, mean durations of fever were 4.6, 5.5, 1.0 and 7.5 days for patients treated with azithromycin, clarithromycin, minocycline and tosufloxacin, respectively (log-rank test, P < 0.0001). Among patients infected with MSMP, mean durations of fever were 2.5, 1.7, 0.9 and 4.3 days for patients treated with azithromycin, clarithromycin, minocycline and tosufloxacin, respectively (log-rank test, P = 0.0162). The MIC90s of azithromycin and clarithromycin among the 27 isolates of MRMP were 64 and 256 μg/ml, respectively, and those among the 23 isolates of MSMP were <0.000125 and 0.001 μg/ml, respectively. The MIC90s of minocycline and tosufloxacin among the 27 isolates of MRMP were 1.0 and 0.25 μg/ml, respectively, and those among the 23 isolates of MSMP were 1.0 and 0.5 μg/ml, respectively.

CONCLUSION

Both minocycline and tosufloxacin showed good in vitro activities against MRMP. Minocycline, but not tosufloxacin, shortened the duration of fever in pediatric patients infected with MRMP compared to the duration of fever in patients treated with macrolides.

A fatal case of melioidosis with pancytopenia in a traveler from Indonesia

Melioidosis, an infectious disease with high mortality, caused by Burkholderia pseudomallei, is endemic in southeast Asia and northern Australia. In Indonesia, autochthonous cases have been rarely reported, with most cases being sporadic and occurring in travelers. Herein, we report a fatal case of neurological melioidosis in a traveler from Indonesia presenting with septic shock.

Cytokine-related and sodium channel polymorphism as candidate predisposing factors for childhood encephalopathy FIRES/AERRPS

Febrile infection-related epilepsy syndrome (FIRES), or acute encephalitis with refractory, repetitive partial seizures (AERRPS), is an epileptic encephalopathy beginning with fever-mediated seizures. The etiology remains unclear. To elucidate the genetic background of FIRES/AERRPS (hereafter FIRES), we recruited 19 Japanese patients, genotyped polymorphisms of the IL1B, IL6, IL10, TNFA, IL1RN, SCN1A and SCN2A genes, and compared their frequency between the patients and controls. For IL1RN, the frequency of a variable number of tandem repeat (VNTR) allele, RN2, was significantly higher in the patients than in controls (p=0.0067), and A allele at rs4251981 in 5' upstream of IL1RN with borderline significance (p=0.015). Haplotype containing RN2 was associated with an increased risk of FIRES (OR 3.88, 95%CI 1.40-10.8, p=0.0057). For SCN1A, no polymorphisms showed a significant association, whereas a missense mutation, R1575C, was found in two patients. For SCN2A, the minor allele frequency of G allele at rs1864885 was higher in patients with borderline significance (p=0.011). We demonstrated the association of IL1RN haplotype containing RN2 with FIRES, and showed a possible association of IL1RN rs4251981 G>A and SCN2A rs1864885 A>G, in Japanese patients. These preliminary findings suggest the involvement of multiple genetic factors in FIRES, which needs to be confirmed by future studies in a larger number of FIRES cases.

Regional Differences in Prevalence of Macrolide Resistance among Pediatric Mycoplasma pneumoniae Infections in Hokkaido, Japan

Recently, macrolide-resistant (MR) Mycoplasma pneumonia appeared, and prevalence of macrolide resistance among M. pneumoniae infections varies by country. However, reports on regional differences in the prevalence of MR M. pneumonia within a country are scarce. In this study, 617 nasopharyngeal swab samples were collected from 617 pediatric patients, and DNA of M. pneumoniae was identified in 95 samples. In 51 of the 95 M. pneumonia positive samples, we detected the presence of mutation A2063G mutation (conferring macrolide resistance) in the 23S rRNA gene. The overall macrolide resistance rate was 53.7%, but there were regional differences: 0.0% in Muroran, 5.3% in Asahikawa, 55.3% in Sapporo, and 100.0% in Kushiro. Statistically significant pairwise differences in the prevalence of MR M. pneumoniae were observed among these cities except for the pair of Muroran and Asahikawa. After exclusion (in order to avoid the influence of macrolides) of patients who were prescribed macrolides before collection of nasopharyngeal swab samples, statistically significant differences persisted: 0.0% in Muroran, 5.6% in Asahikawa, 38.5% in Sapporo, and 100.0% in Kushiro.

A case of severe progressive early-onset epileptic encephalopathy: unique GABAergic interneuron distribution and imaging

Early-onset epileptic encephalopathies include various diseases such as early-infantile epileptic encephalopathy with suppression burst. We experimentally investigated the unique clinicopathological features of a 28-month-old girl with early-onset epileptic encephalopathy. Her initial symptom was intractable epilepsy with a suppression-burst pattern of electroencephalography (EEG) from 7 days of age. The suppression-burst pattern was novel, appearing during sleep, but disappearing upon waking and after becoming 2 months old. The EEG showed multifocal spikes and altered with age. Her seizures demonstrated various clinical features and continued until death. She did not show any developmental features, including no social smiling or head control. Head MRI revealed progressive atrophy of the cerebral cortex and white matter after 1 month of age. (123)IMZ-SPECT demonstrated hypo-perfusion of the cerebral cortex, but normo-perfusion of the diencephalon and cerebellum. Such imaging information indicated GABA-A receptor dysfunction of the cerebral cortex. The genetic analyses of major neonatal epilepsies showed no mutation. The neuropathology revealed atrophy and severe edema of the cerebral cortex and white matter. GAD-immunohistochemistry exhibited imbalanced distribution of GABAergic interneurons between the striatum and cerebral cortex. The results were similar to those of focal cortical dysplasia with transmantle sign and X-linked lissencephaly with ARX mutation. We performed various metabolic examinations, detailed pathological investigations and genetic analyses, but could not identify the cause. To our knowledge, her clinical and pathological courses have never been described in the literature.

[A case of melioidosis occurring after a long-term stay in Vietnam that developed pulmonary cavitation and relapsed with multiple pulmonary nodules]

A 69-year-old man complained of fever in September 2009, after returning from Vietnam where he has been working for 20 years. He had diabetes mellitus and was on diabetic oral medication. He was examined at a nearby hospital, and found out to have pneumonia with cavity formation in the right upper lobe which was found out to be not due to tuberculosis. Although the patient once recovered with antibacterial medicine, after a few months, in January 2010, he was admitted to our hospital because of recurrent fever. Computed tomography revealed multiple pulmonary nodules which were thought to be pulmonary emboli, as well as subcutaneous abscess, spleen abscess, and kidney abscess. Blood test showed that he also had DIC. As Burkholderia pseudomallei was cultured from the subcutaneous abscess and blood, was diagnosed as melioidosis. The patient was treated with meropenem for 8 weeks, and then a maintenance oral antibacterial medicine was continued for the next 6 months. The patient fully recovered after those treatments and has not relapsed since then. This is the ninth case report of melioidosis in Japan which is an imported infectious disease.

An outbreak of histoplasmosis among healthy young Japanese women after traveling to Southeast Asia

Histoplasmosis, caused by Histoplasma capsulatum, is an endemic mycosis in many countries of the world except for Japan. Outbreaks of histoplasmosis among Japanese people are very rare and are mainly imported by travelers. We report an outbreak of histoplasmosis among healthy Japanese people who traveled to a resort area in Southeast Asia. Three young Japanese women traveled to Langkawi island, Malaysia and stayed on the island for five days without visiting caves, a known reservoir of H. capsulatum. All three individuals developed flu-like symptoms with multiple nodule shadows on chest X rays or chest CT scans at around ten days after their return to Japan. Serum samples obtained from the three subjects were positive for anti-Histoplasma antibody and specific PCR for H. capsulatum on lung biopsy specimens and the serum from one patient was positive. The clinical course of all three patients improved without the use of anti-fungal agents and no recurrence has been confirmed. Clinical attendants should consider histoplasmosis when they see patients with flu-like symptoms with abnormal chest X-rays after visiting H. capsulatum endemic areas, especially Southeast Asia.

Identification of a site-specific tyrosine recombinase that mediates promoter inversions of phase-variable mpl lipoprotein genes in Mycoplasma penetrans

Mycoplasma penetrans has the ability to change its surface lipoprotein profiles frequently. The P35 family lipoproteins encoded by the mpl genes are key players in this profile variation. The M. penetrans HF-2 genome has 38 mpl genes that form three gene clusters. Most of these mpl genes have an invertible promoter sequence that is responsible for the ON/OFF switching of individual mpl gene expression. Here, we identified the recombinase that catalyses inversions of the mpl gene promoters. We focused on two open reading frames of the M. penetrans HF-2 genome, namely MYPE2900 and MYPE8180, which show significant homology to the tyrosine site-specific recombinase (Tsr) family proteins. Since genetic tools for M. penetrans are still not developed, we cloned the MYPE2900 and MYPE8180 genes and expressed them in Mycoplasma pneumoniae and Escherichia coli. The promoter regions of the mpl genes [p35 (MYPE6810) or p42 (MYPE6630) genes] were also introduced into M. pneumoniae and E. coli cells expressing MYPE2900 or MYPE8180. Inversion of these promoters occurred in the presence of the MYPE2900 gene but not in the presence of the MYPE8180 gene, indicating that the MYPE2900 gene product is the recombinase that catalyses mpl gene promoter inversions. We used a PCR-based method to detect mpl promoter inversion. This method also enabled us to detect inversions of 10 mpl gene promoters in M. penetrans HF-2 cells. All these promoter inversions occurred at the 12 bp inverted repeat (IR) sequences flanking the promoter sequence. The consensus sequence of these IRs was proposed as TAAYNNNDATTA (Y=C or T; D=A, G or T).

Characterization and molecular analysis of macrolide-resistant Mycoplasma pneumoniae clinical isolates obtained in Japan

In recent years, Mycoplasma pneumoniae strains that are clinically resistant to macrolide antibiotics have occasionally been encountered in Japan. Of 76 strains of M. pneumoniae isolated in three different areas in Japan during 2000 to 2003, 13 strains were erythromycin (ERY) resistant. Of these 13 strains, 12 were highly ERY resistant (MIC, > or =256 microg/ml) and 1 was weakly resistant (MIC, 8 microg/ml). Nucleotide sequencing of domains II and V of 23S rRNA and ribosomal proteins L4 and L22, which are associated with ERY resistance, showed that 10 strains had an A-to-G transition at position 2063 (corresponding to 2058 in Escherichia coli numbering), 1 strain showed A-to-C transversion at position 2063, 1 strain showed an A-to-G transition at position 2064, and the weakly ERY-resistant strain showed C-to-G transversion at position 2617 (corresponding to 2611 in E. coli numbering) of domain V. Domain II and ribosomal proteins L4 and L22 were not involved in the ERY resistance of these clinical M. pneumoniae strains. In addition, by using our established restriction fragment length polymorphism technique to detect point mutations of PCR products for domain V of the 23S rRNA gene of M. pneumoniae, we found that 23 (24%) of 94 PCR-positive oral samples taken from children with respiratory infections showed A2063G mutation. These results suggest that ERY-resistant M. pneumoniae infection is not unusual in Japan.

Use of fluorescent-protein tagging to determine the subcellular localization of mycoplasma pneumoniae proteins encoded by the cytadherence regulatory locus

Mycoplasma pneumoniae lacks a cell wall but has internal cytoskeleton-like structures that are assumed to support the attachment organelle and asymmetric cell shape of this bacterium. To explore the fine details of the attachment organelle and the cytoskeleton-like structures, a fluorescent-protein tagging technique was applied to visualize the protein components of these structures. The focus was on the four proteins--P65, HMW2, P41, and P24--that are encoded in the crl operon (for "cytadherence regulatory locus"), which is known to be essential for the adherence of M. pneumoniae to host cells. When the P65 and HMW2 proteins were fused to enhanced yellow fluorescent protein (EYFP), a variant of green fluorescent protein, the fused proteins became localized at the attachment organelle, enabling visualization of the organelles of living cells by fluorescence microscopy. The leading end of gliding M. pneumoniae cells, expressing the EYFP-P65 fusion, was observed as a focus of fluorescence. On the other hand, when the P41 and P24 proteins were labeled with EYFP, the fluorescence signals of these proteins were observed at the proximal end of the attachment organelle. Coexpression of the P65 protein labeled with enhanced cyan fluorescent protein clearly showed that the sites of localization of P41 and P24 did not overlap that of P65. The localization of P41 and P24 suggested that they are also cytoskeletal proteins that function in the formation of unknown structures at the proximal end of the attachment organelle. The fluorescent-protein fusion technique may serve as a powerful tool for identifying components of cytoskeleton-like structures and the attachment organelle. It can also be used to analyze their assembly.

Multiple promoter inversions generate surface antigenic variation in Mycoplasma penetrans

Mycoplasma penetrans is a newly identified species of the genus MYCOPLASMA: It was first isolated from a urine sample from a human immunodeficiency virus (HIV)-infected patient. M. penetrans changes its surface antigen profile with high frequency. The changes originate from ON<==>OFF phase variations of the P35 family of surface membrane lipoproteins. The P35 family lipoproteins are major antigens recognized by the human immune system during M. penetrans infection and are encoded by the mpl genes. Phase variations of P35 family lipoproteins occur at the transcriptional level of mpl genes; however, the precise genetic mechanisms are unknown. In this study, the molecular mechanisms of surface antigen profile change in M. penetrans were investigated. The focus was on the 46-kDa protein that is present in M. penetrans strain HF-2 but not in the type strain, GTU. The 46-kDa protein was the product of a previously reported mpl gene, pepIMP13, with an amino-terminal sequence identical to that of the P35 family lipoproteins. Nucleotide sequencing analysis of the pepIMP13 gene region revealed that the promoter-containing 135-bp DNA of this gene had the structure of an invertible element that functioned as a switch for gene expression. In addition, all of the mpl genes of M. penetrans HF-2 were identified using the whole-genome sequence data that has recently become available for this bacterium. There are at least 38 mpl genes in the M. penetrans HF-2 genome. Interestingly, most of these mpl genes possess invertible promoter-like sequences, similar to those of the pepIMP13 gene promoter. A model for the generation of surface antigenic variation by multiple promoter inversions is proposed.

The complete genomic sequence of Mycoplasma penetrans, an intracellular bacterial pathogen in humans

The complete genomic sequence of an intracellular bacterial pathogen, Mycoplasma penetrans HF-2 strain, was determined. The HF-2 genome consists of a 1 358 633 bp single circular chromosome containing 1038 predicted coding sequences (CDSs), one set of rRNA genes and 30 tRNA genes. Among the 1038 CDSs, 264 predicted proteins are common to the Mycoplasmataceae sequenced thus far and 463 are M.penetrans specific. The genome contains the two-component system but lacks the essential cellular gene, uridine kinase. The relatively large genome of M.penetrans HF-2 among mycoplasma species may be accounted for by both its rich core proteome and the presence of a number of paralog families corresponding to 25.4% of all CDSs. The largest paralog family is the p35 family, which encodes surface lipoproteins including the major antigen, P35. A total of 44 genes for p35 and p35 homologs were identified and 30 of them form one large cluster in the chromosome. The genetic tree of p35 paralogs suggests the occurrence of dynamic chromosomal rearrangement in paralog formation during evolution. Thus, M.penetrans HF-2 may have acquired diverse repertoires of antigenic variation-related genes to allow its persistent infection in humans.

Suppression of specific IgE antibody responses by liposome-conjugated ovalbumin in mice sensitized with ovalbumin via the respiratory tract

BACKGROUND

Previously we have shown that intranasal administration of ovalbumin (OVA) together with cholera toxin (CT) abrogates nasal tolerance to OVA, resulting in the induction of specific IgE antibody (Ab) responses, and that intraperitoneal injection of OVA coupled with liposomes (OVA-liposomes) induces a selective suppression of IgE Ab responses to OVA. Whether OVA-liposomes suppress anti-OVA IgE Ab responses in mice sensitized with CT-combined OVA via the respiratory tract remains to be clarified.

METHODS

In some experiments, mice were given OVA, liposomes or OVA-liposomes with or without CT intranasally three times, at 2-week intervals (weeks 0, 2 and 4). In other experiments, mice were given OVA-liposomes intranasally 2 days before or 1 and 3 weeks after CT-combined OVA (week 0), which was administered intranasally three times, at 2-week intervals (weeks 0, 2 and 4). Two weeks after the third administration of CT-combined OVA (week 0), nasal wash and serum IgA, IgG and IgE Ab responses were assayed.

RESULTS

Pretreatment with OVA-liposomes suppressed IgE Ab responses to CT-combined OVA, with a significantly high production of both nasal IgA and serum IgG Abs. Moreover, treatment with OVA-liposomes 1 and 3 weeks after CT-combined OVA administration also suppressed IgE Ab responses. The suppression of anti-OVA IgE Ab production by OVA-liposomes was accompanied by a simultaneous enhancement of specific IgA and IgG (IgG1, and especially IgG2a) Ab production.

CONCLUSIONS

Postimmunization treatment with OVA-liposomes, as well as preimmunization treatment, suppressed specific IgE Ab responses in mice sensitized intranasally with CT-combined OVA. Allergens conjugated to liposomes may be appropriate for preventing the development of allergies to inhaled or dietary antigens in humans.

Antigen-specific, IgE-selective unresponsiveness induced by antigen-liposome conjugates. Comparison of four different conjugation methods for the coupling of antigen to liposome

BACKGROUND

We have previously reported that ovalbumin (OVA) coupled with liposome via glutaraldehyde (GA) induced OVA-specific- and IgE-selective unresponsiveness in mice.

METHODS

In this study, OVA-liposome conjugates were made using four different coupling protocols: via GA, N-(6-maleimidocaproyloxy) succinimide (EMCS), disuccinimidyl suberate (DSS) and N-succimidyl-3(2-pyridyldithio)propionate (SPDP) and the induction of antigen-specific IgG and IgE antibody production was investigated for each. In addition, antigen-specific cytokine production by spleen cells of mice immunized either with OVA-liposome or with OVA adsorbed with aluminum hydroxide was investigated.

RESULTS

OVA-liposome conjugates coupled via GA or DSS did not induce anti-OVA IgE antibody production but induced substantial anti-OVA IgG antibody production. On the other hand, the induction of anti-OVA IgE unresponsiveness by OVA-liposome conjugates coupled via EMCS or SPDP was incomplete. The amount of interleukin 4 (IL-4) produced by spleen cells stimulated in vitro with OVA correlated well with anti-OVA IgE antibody production in donor mice. However, the production of no other cytokine, i.e., IL-2, IL-5, IL-10 or interferon-gamma, was correlated with in vivo IgE antibody production.

CONCLUSION

OVA-liposome coupled via GA or DSS induced complete suppression of anti-OVA IgE production. The results in this study further suggest that the regulation of IgE antibody production does not necessarily correlate with so-called Th1 cytokine production.

Delayed progression of murine AIDS in C57BL/6 mice pre-immunized with a highly antigenic 10-mer peptide encoded by the murine AIDS defective virus gag p12 gene

C57BL/6 (B6) mice were immunized with a highly antigenic 10-mer peptide (P12-10), which is encoded by the murine AIDS (MAIDS) defective virus gag p12 gene, emulsified in incomplete Freund's adjuvant (ICFA). One week later, the mice were inoculated with the MAIDS virus to see if the immunization affects progression of MAIDS. It was demonstrated that the immunization significantly delayed progression of MAIDS, although it failed to induce appreciable cytotoxic T lymphocyte (CTL) responses against the P12-10 antigen. In contrast, immunization of B6 mice with the P12-10 coupled with liposome induced substantial CTL responses but failed to protect the mice against MAIDS development. This segregation between CTL activity and in vivo protection efficacy might be worth considering when we exploit vaccines for augmenting cellular immunity mediated by CD8+ T cells.

Macrophage inhibition of lymphocyte and tumor cell growth is mediated by 25-hydroxycholesterol in the cell membrane

We have previously reported that a lipid molecule in the membrane fraction of cloned macrophage hybridomas inhibited the growth of lymphocytes and several tumor cell lines. In this study, the inhibitory lipid molecule in the membrane fraction of macrophages was analyzed by thin-layer chromatography and identified as 25-hydroxycholesterol, a family of oxysterols. This conclusion was confirmed by analysis using gas chromatography-mass spectrometry. In addition, both 25-hydroxycholesterol and the lipid molecule recovered from macrophage cell membrane induced apoptosis of the murine T cell lymphoma, BW-5147. These results suggest that an oxysterol expressed in the macrophage cell membrane may participate in the regulation of cell growth through cell contact.

Induction of protection against oral infection with cytotoxin-producing Escherichia coli O157:H7 in mice by shiga-like toxin-liposome conjugate

We have previously reported that purified Shiga-like toxins (SLT), SLT-I and SLT-II coupled with liposomes induced a substantial amount of anti-SLT-I and anti-SLT-II IgG antibody production, respectively, in mice. The levels of anti-SLT antibody in the sera of SLT-liposome-immune mice correlated well with the protection against subsequent challenge with SLT. In this study, mice were immunized intraperitoneally with the mixture of SLT-I-liposome and SLT-II-liposome and protection against oral infection with cytotoxin-producing Escherichia coli O157:H7 was evaluated. All of the mice that received immunization with the mixture of SLT-I-liposome and SLT-II-liposome were protected against subsequent intravenous challenge with 10 LD50 of either SLT-I or SLT-II. Eight weeks after primary immunization, mice were inoculated intragastrically with 10(9) CFU of E. coli O157:H7 strain 96-60. All SLT-liposome-immune mice tested survived without any apparent symptom while control mice died within 5 days. In addition, as shown by other antigen-liposome conjugates, SLT-liposome induced undetectable anti-SLT IgE antibody production while they induced substantial amounts of anti-SLT IgG antibodies. These results suggest that SLT-liposome conjugate may serve as a candidate vaccine that induces protection against cytotoxin-producing E. coli infection.

Induction of protection against tetanus toxin in mice by tetanus toxoid-liposome conjugate

Tetanus toxoid (Ttd) was coupled to liposomes via glutaraldehyde. Intraperitoneal injection in BALB/c mice with Ttd-liposomes induced a substantial amount of anti-Ttd IgG antibody production and an extremely low level of anti-Ttd IgE antibody production. Mice immunized with Ttd-liposomes were successfully protected against a subsequent challenge with a lethal dose of tetanus toxin (Ttx). On the other hand, aluminum hydroxide-adsorbed Ttd (Ttd-alum) and plain Ttd solution induced the production of both IgG and IgE antibodies against Ttd. Moreover, secondary immunization with Ttd-liposomes in mice, in which anti-Ttd IgE antibody production was induced by Ttd-alum led to enhanced anti-Ttd IgG and a limited anti-Ttd IgE antibody production. When Ttd-liposome preparation was lyophilized, the efficacy of Ttd-liposomes was maintained for 6 months at 37 C, suggesting that this vaccine preparation would be stable without refrigeration. These results demonstrate the potential ability of Ttd-liposome conjugates to produce a tetanus vaccine which provides protection against (Ttx) while inducing the least amount of anti-Ttd IgE antibodies.

Ovalbumin coupled either with murine red blood cells or liposome induces IgG but not IgE antibody production

Ovalbumin (OVA) was coupled with murine red blood cells (MRBC) using glutaraldehyde. The OVA-MRBC conjugate induced anti-OVA IgG antibody in mice at almost the same level as OVA in alum. However, no IgE antibody production specific for OVA was observed in OVA-MRBC-injected mice. A significant increase in IGG2a production was obtained with OVA-MRBC immunization, whereas the production of IgG1 predominated in OVA in alum immunization. Am OVA-liposome conjugate induced IgE-specific unresponsiveness in mice in the same manner as OVA-MRBC. Similar results were obtained when antigens other than OVA, such as tetanus toxoid or diphtheria toxoid, were coupled to liposome. These results show the potential of antigen-liposome conjugates for the development of vaccine that induces sufficient IgG antibody production without IgE synthesis.

Inhibition of tumor cell growth by murine splenic adherent cells stimulated with IFN-gamma

We have previously reported that the growth of lymphocytes and tumor cells with lymphocyte lineage was strongly inhibited by a part of cloned macrophage hybridomas. This growth inhibition was accomplished by cell-to-cell contact and found to be attributed to lipid-like molecule(s) in a macrophage hybridoma cell membrane fraction. Instead of macrophage hybridomas, in the present study we utilized splenic adherent cells (SACs) that had been stimulated with IFN-gamma to see whether they inhibited tumor cell growth or not. The results demonstrated that IFN-gamma-stimulated but not unstimulated SACs showed a significant growth inhibition of BW-5147 tumor cells. This growth inhibition was not mainly mediated by prostaglandin E2 secreted from macrophages, since the inhibition was not reduced in the presence of indomethacin. Furthermore, as was reported previously in the case of macrophage hybridomas, the inhibitory activity resides in a lipid fraction of IFN-gamma-stimulated SAC membrane.

Protection against verocytotoxin in mice induced by liposome-coupled verocytotoxin

Purified verocytotoxins (VTs), VT1 and VT2, were coupled to liposomes via glutaraldehyde. During the coupling procedure, both VT1 and VT2 were detoxified. Intraperitoneal injection in BALB/c mice with either VT1-liposome or VT2-liposome induced a substantial amount of anti-VT1 or anti-VT2 IgG antibody production, respectively. Mice immunized with VT2-liposome were protected against intravenous challenge with a lethal dose of VT2 and the degree of protection correlated well with the amount of IgG induced against VT2. Although VT1-liposome failed to induce protection against VT1, the decrease of the body weight observed after the toxin challenge correlated inversely with the amount of anti-VT1 IgG induced, suggesting that VT1 neutralizing antibody was present in VT1-liposome-immune mice. In addition, VT-liposome conjugate induced no detectable anti-VT IgE antibody production. These results demonstrate the potential ability of VT-liposome conjugates for the production of VT vaccine which induces protection against VTs.

Differential stimulation requirements for IL-12 production among clones of macrophage hybridomas

We have previously established cloned macrophage hybridomas by somatic cell fusion of the macrophage tumor P388D1 of DBA/2 (H-2d) origin with splenic adherent cells of CKB mice (H-2k). Several cloned lines displayed the serologic and functional characteristics of macrophages. In this study, we evaluated the ability of these hybridomas to produce IL-12 after combined stimulation with IFN-gamma and lipopolysaccharide (LPS). The patterns of IL-12 production by these cloned macrophages fell into three groups. The first group produced IL-12 on stimulation with LPS in combination with IFN-gamma pretreatment, the second group produced IL-12 on stimulation with LPS regardless of the pretreatment with IFN-gamma, and the third group did not produce IL-12 at all on stimulation with IFN-gamma and LPS. None of the macrophage clones tested produced IL-12 constitutively. The results correlated well with IL-12 p40 mRNA expression in those macrophages as detected by RT-PCR. These results suggest the differential stimulation requirements for IL-12 production among macrophages at a clonal level.

Application of PCR for detection of mycoplasma DNA and pestivirus RNA in human live viral vaccines

PCR techniques were applied for the detection of mycoplasma DNA and pestivirus RNA to 43 lots of live viral vaccines (measles, mumps, rubella, and oral poliomyelitis) produced by six manufacturers in Japan. Although mycoplasma DNA was not detected in any of the vaccines tested, pestivirus RNA was detected in 12 lots (28%). The incidence of contamination among the four viral vaccines was in the range of 20 to 37%, and the incidence among the six manufacturers varied from 0 to 56%.

Biotin deficiency in an infant fed with amino acid formula and hypoallergenic rice

An amino acid formula produced in Japan is not supplemented with biotin since biotin is not permitted as a food additive. Biotin deficiency developed in an 11-month-old Japanese infant who had been diagnosed as a neonate with cow milk and soy bean allergy and fed with an amino acid formula and hypoallergenic rice processed by protease. Serum levels of zinc, essential fatty acids and biotinidase were within the normal range while that of biotin was below the normal range. Urinary 3-hydroxy-isovalerate and slightly elevated levels of plasma branched-chain amino acids disappeared 1 week after oral supplementation with 1 mg day-1 of biotin as did the symptoms of orificial skin lesions, lethargy, hypotonia and alopecia later. In summary, to prevent biotin deficiency, biotin should be added to the Japanese amino acid formula.

Evaluation of current sterility tests for human live viral vaccines

Current sterility tests for human viral vaccines were evaluated. A total of 43 lots of bulk suspension of live viral vaccines (measles, mumps, rubella and oral poliomyelitis) produced by six manufacturers in Japan were evaluated for bacteriostatic and mycoplasmastatic activities. Some of them showed fairly high bacteriostatic and mycoplasmastatic activities, due to antibiotics added during vaccine production. It was concluded that the current sterility test for mycoplasmas is not reliable to detect viable mycoplasmas in live viral vaccines.

Ovalbumin-liposome conjugate induces IgG but not IgE antibody production

Antibody response after immunization with surface-coupled ovalbumin (OVA) of liposomes was investigated in mice. OVA was coupled to the surface of liposome via amino groups using glutaraldehyde. OVA-liposome conjugate induced a significant anti-OVA IgG antibody production in mice. However, no IgE antibody production specific for OVA was observed. Immunization with OVA-liposome induced IgE-specific unresponsiveness even after the subsequent challenge with OVA adsorbed with with aluminium hydroxide (OVA-alum), which induces a high level of IgE antibody production. Furthermore, following the primary immunization with OVA-alum, a secondary challenge with OVA-liposome boosted anti-OVA IgG but not anti-OVA IgE antibody production. These results show the potential of the antigen-liposome conjugate for the development of a vaccine with the least allergic reaction and also for the application of immunotherapy.

IgE-specific unresponsiveness in mice induced by ovalbumin coupled with murine red blood cells

Ovalbumin (OVA) was coupled with murine red blood cells (MRBC) using glutaraldehyde. OVA-MRBC conjugate induced anti-OVA IgG antibody production in mice at almost the same level as OVA in alum. However, no IgE antibody production specific for OVA was observed in OVA-MRBC-injected mice. IgE-specific unresponsiveness was also observed in mice injected with OVA coupled with sheep red blood cells (OVA-SRBC), suggesting that our present observation was not restricted to the property of MRBC. These results show the potential ability of antigen-RBC conjugate for the development of vaccine that induces sufficient IgG antibody production without IgE synthesis.